Paper size



Patented Feb. 13, 1951 j-uNlrEo STATES PATENTOFFICE'.

to P. H. Glatfelter Company, Spring Grove, Pa... a corporation of Pennsylvania No Drawing.-

This invention relates to paper making and more particularly to anovel paper sizing composition and a method of making the size.

In the manufacture of papers that are resistant to ink and water penetration it has long been customary to incorporate in the paper stock that is to be used in making the paper a size that is adapted to inhibit the flow of ink and other liquids into the fibers of thepaper. One widely used size comprises a relatively dilute alkaline dispersion or solution ofrosin in water.

.The size is commonly incorporated into the paper stock in' the beating'operation prior to the forming of the paper into a sheet and a paper-makers alum is added to cause the rosin to be precipitated upon the fibers'of the'paper stock.

i The conventional rosin size is subject to a number of disadvantages. When such a conventional size is used the results are, at times, somewhat erratic, that is, the degree of resistance to ink penetration of .the sized paper is non-uniform across or along the sheet. Also With certain types of paper there is a limit to the degree of sizing that can be obtained in that as the quantity of 'size is increased a point is reached-at which iurther additionsof size do not produce any increase in the resistance of the paper to ink penetration. Because of this limiting factor there are some cases in which it is not possible to obtain the desired sizing effect with a conventional rosin size. Moreover the large amounts of rosins present'inhard-sized papers tend to lower the quality of the paper.

It is accordingly an object'of the present invention: to provide a paper size composition capable of overcoming the disadvantages of the conventional size. It is another object of the invention to provide a paper size that is capable 'of producing-a relatively high degree of resistance to ink and water penetration. .It is a further object of the invention to provide a paper size that can be used in substantially smaller amounts than the conventional rosin sizes and produce an equivalent sizing efiect. It is still another object of the invention to provide a method of making such a size. Qther objects and advantages of the inventionwill be in'pa'rt obvious and in part pointed out: hereafter.

The objectsand advantagesof the present invention maybe achieved, in general, by incorporatingin a paper size a quantity of a resin formed from polyhydric alcohol and a polybasic acid, the character of the resin beingsuch that .it has a r elativelyhiglh acid number. It has been found that penetration of ink through the pa er and Application January 14, 1941, Serial No. 722,071 7 10' Claims. (01. 260-26) spreading of ink along the surface of the paper may be inhibitedby flocculating the coloring matter of the ink and that such flocculationof the coloring matter of the ink can be effectively produced by substances which have. relatively high acid numbers, i. e., a relatively large number of acidic groups per unit molecular Weight of the substance. Thus a suitable substance with a sufiici'ently high acid number when incorporated in a size under the proper conditions and applied to a sheet of paper will effectively increase the resistance of the paper to ink penetration.

It isevidentv that. all substances having high acid numbers cannot be used since it is necessary that the. substance used have not only a high acid number but that it also have chemical andphysical properties which permit its eifective incorporation in the paper without adversely affecting desirable properties of the paper other than resistance to ink penetration. It has been found that esters of polyhydric alcohols and polybasic acids, either in. monomeric or polymeric form and having acid numbers of at least about 250 may be incorporated in a'paper size which when applied to paper produces a material improvement'in the resistance of the paper to ink penetration, It hasbeen. further found that a anhydride'copolymer is such that it can bev used in relatively small quantities and may, with ad'- vantage, be admixed with a relatively large'pro portion of rosin of paper making grade. The mixture of copolymer and rosin maythen be dispersed in the usual manner and applied. the paper during the beating operation in the usual way.

In order to point out more fully the nature of the present invention the following specific ex.- ampleis given of a preferred method of compounding the size of the presentinvention; It

isto be understood that the procedure set forth f is illustrative only and may be modified in various ways as desired.

A mixtureiis'prepared of 305 pounds of rosin" of paper making grade and 25 pounds of a copoly mer of glycerol and maleic anhydride having an acid number in excess of 350. The temperature of the mixture is raised to 140 to 150 C. to ensure complete melting of the ingredients and the resin mixture is then mixed vigorously by me chanical agitation. The resulting mixture is neutralized with an alkaline solution made up by dissolving 60 pounds of soda ash in 20 gallons of water. The alkaline solution is' added to the mixture slowly with continuous agitation and with the simultaneous addition of water that has been heated to a temperature of 70 to 80 C. The hot Water is added to prevent the mixture from getting too 'thick and the quantity added is that amount which is sufiicient to keep the mixture in a conveniently fluid condition.

When all of the alkali has been added the mix.v

ture is further diluted with hot Water at 70 to 80 aqueous alkaline dispersion of a mixture of rosin C. to a total volume of approximately 100 ga1lons and it is then further diluted with either warm or cold water to a total volume of 330 gallons.

The resulting size dispersion or s'olutioncontains about 12% by weight of solids or roughly one pound per gallon, and its pH is approximately 9. The size as thus prepared is in condition to be added to the beater in the usual way.

It may be pointed out that useful products are obtained in various intermediate stages of the foregoing procedure. and copolymer may be cooled until it solidifies and stored as such for later use or it may be shipped to a point at which it is to be used and subsequently neutralized and dispersed in water. Also the size may be stored or shipped in relatively concentrated form and diluted to its final concentration at the time that it is to be used.

The quantity of the copolymer admixed with the rosin may be varied through a relatively wide range. I have found that desirable results are obtained by incorporating from about 5% to about 25% by Weight of copolymer in the rosincopolymer mixture. Within this range of proportions the composition'that I prefer to use comprises about 10% by weight of the copolymer and 99% by weight of the rosin.

ltihas been found that a size prepared as described above is substantially more effective than conventional rosin sizes in inhibiting penetration of ink into papers that have been sized therewith. .A variety of papers sized with the size of the present invention have been tested by a standard ink penetration test and it has been found that the precise degree of improvement varies somewhat with the type of paper to which the size is applied. However an appreciable increase in ink penetration resistance was found in the case of all papers tested and in some cases the'ink resistance was more than double that obtained with a conventional rosin size when corresponding quantities of the two sizes were used.

Thus it is possible to use substantially smaller quantities of the present size and still obtain a sizing efiect equivalent tothat obtained with a conventional rosin size.

Since many embodiments might be made of the present invention and since many changes might be made in the embodiment disclosed herein, it is Thus the mixture of rosin dride, said copolymer being present to the extent of between 5% and 25% by Weight of said mixture and the degree of polymerization of said copolymer being sufficiently low that the acid number of said copolymer is greater than 350.

4. A paper size composition comprising an and a copolymer of glycerol and maleic anhydride, said copolymer being present to the extent of about 10% by weight of said mixture and the degree of polymerization of said copolymer being sufiiciently low that the acid number of said copolymer is greater than 350.

5. A paper size composition comprising an aqueous alkaline dispersion containing about 12% by weight of a mixture of rosin and a copolymer of glycerol and maleic anhydride, the degree of polymerization of said copolymer being sufficiently low that the acid number of said copolymer is greater than 350.

6. A paper size composition comprising a mixture of rosin and a copolymer of glycerol and maleic anhydride, the degree of polymerization of said copolymer being sufilciently low that the acid number of said copolymer is greater than 350. g

7. A paper size composition comprising a mixture of rosin and a copolymer of glycerol and maleic anhydride, said copolymer being present to the extent of between 5% and 25% by weight of said mixture and the degree of polymerization of said copolymer being sufficiently low that the acid number of said copolymer is greater than 8. A paper size composition comprising a mix- I ture of rosin and a copolymer of gylcerol and ization that its acid number is greater than 350 and adding to said molten mixture an aqueous solution of an alkali to disperse said mixture.

10. A paper size composition comprising an aqueous alkaline dispersion of a copolymer of 1: glycerol and maleic anhydride, the degree of polymerization of said copolymer being sufficiently low that the acid number of saidcopolymer is greater than 350.

AUGUST S. ERSPAMER.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,413,144 Weisberg Apr. 18, 1922 1,780,375 I Bradley Nov. 4, 1930 Certificate of Correction Patent No. 2,541,692 February 13, 1951 AUGUST S. ERSPAMER It is hereby certified that error appears in the printed specification of the above numbered patent requiring correctlon as follows:

Column 2, line 84 after the Word copolymer insert anal becomes smaller as the degree of polymerization increases. H enee it is desirable that the copolymer;

and that the said Letters Patent should be read as corrected above, so that the same may conform to the record of the case in the Patent Office.

Signed and sealed this 5th day of June, A. D. 1951.

THOMAS F. MURPHY,

Assistant Oommz'ssz'cmer of Patents. 

1. A PAPER SIZE COMPOSITION COMPRISING AN AQUEOUS ALKALINE DISPERSION OF A MIXTURE OF ROSIN AND AN ESTER OF GLYCEROL AND MALEIC ANHYDRIDE, SAID ESTER HAVING AN ACID NUMBER OF AT LEAST
 250. 